The invention relates generally to removal and prevention of undesired growths of moss and the like from rooftops, buildings and other outside surfaces exposed to the atmosphere and more particularly to an improved method and product for biocidal treatment of such surfaces.
In very moist climates, the growth of moss, mildew, and other organisms on shaded surfaces, such as rooftops, buildings, walkways, patios, driveways, and grass, is a problem. Such growths are unsightly, do not permit the surface to dry, and can cause a variety of problems depending on the nature of the surface. In particular, moss growth on rooftops does not allow the roof to dry properly and eventually causes accelerated decomposition of the shingles. This permits water leakage which can damage the roof support structure and ceiling materials below. The resultant damage is very expensive to repair. Similarly, moss growth along expansion joints and in cracks on concrete surfaces, such as patios and driveways, is unsightly, fosters additional undesired microbial growth, and accelerates decomposition of the concrete. It can also be slippery when wet, increasing the risk of injury to users. Moss growth in lawns and in gardens also is unsightly, competes with the grass, and fosters weed and other undesired microbial growth. Consequently, it is desirable to kill moss growing on each of these surfaces and to prevent its return.
Manual removal of moss from rooftops is difficult, dangerous, and provides only a temporary solution to the problem. The moss regrows within a short time from spores in the air and beneath the shingles. Similarly, removal of moss from the cracks in concrete surfaces is temporary as spores will inevitably be left behind or fly through the air which will permit regrowth within a short period of time. Mechanical removal of moss from grass is virtually impossible, at least without damaging the lawn and in most cases instead of removing the moss it is just being transplanted.
Various attempts have been made to control moss growth chemically, what I mean by chemically is that metals have been reduced to the salt form by the use of such acids as hydrochloric acid. Certain metallic salts, such as lead, iron, zinc, and copper-sulfur compounds, have been used with varying degrees of success but also with numerous drawbacks. Powdered compounds, such as copper sulfate, can be sprinkled dry on a roof; but the application is usually uneven and will burn, and as it washes off the roof it will kill grass, trees, plants and ornamental plants. It washes off within a few weeks or on the next rain and requires frequent reapplication. Water solutions of zinc or ferrous sulfate can be applied more evenly than the powders of such compounds but likewise require frequent reapplication and burn when they run off. Such solutions can also harm a person's skin, necessitating precautions during application. Ferrous sulfate has the further disadvantage that it stains concrete, roofs, tile and cloth surfaces. Such compounds are also unsuitable for lawns and gardens because they tend to burn the grass and garden plants, and one has to watch out not to get any on the walkways of concrete.
Lime is frequently used on grass and in gardens to suppress moss growth. However, it too stains concrete and so cannot be used on patios or on roofs because it would start rot. Moreover, it raises the pH of the soil which is undesirable for many applications.
Rooftops have also been treated with metal strips. For example, nailing a flat strip of copper to a roof has been tried but has proven unsatisfactory for treating established moss growths. It can take many months before natural erosion of the strips by rain releases enough metal ions to begin killing the moss. S. L. Rapaport has previously proposed, in U.S. Pat. No. 3,479,130, mounting flat bimetallic strips horizontally along a rooftop to inhibit microbial or fungal growths which darken rooftops in semitropical or tropical climates. Rapaport's bimetallic strips comprise two metals, such as copper and lead, between which an electrolytic reaction is said to result when rainwater contacts the metal. According to Rapaport, such reaction dissolves ions of the metals into the water to create a solution which kills the microbes and fungus. To obtain adequate coverage of a rooftop, multiple strips are vertically spaced four to ten shingles apart. However, it can take several months before any reduction in moss occurs, if any. Also, installing such strips is time-consuming and results in an aesthetically unappealing horizontally striped appearance of the roof, and the rain may not come into contact, or it may rain too much, or it may not rain enough or not at all.
My U.S. Pat. No. 4,276,732 describes a device for killing moss on rooftops comprising an elongated bimetallic trough for horizontal positioning along a rooftop to catch rainwater. The rainwater contacts layers or chips of copper and lead as it flows through holes at the top of the trough. The resultant electrolyte flows down the rooftop and kills the moss. Such a device is an improvement over Rapaport but is still aesthetically unappealing, expensive, and time-consuming to install.
None of the foregoing metal devices is usable on a horizontal surface; and so they cannot be used on lawns, patios, trees, sidewalks, or driveways. Practical considerations of the normal usage of such surfaces further preclude using strips or troughs on lawns, sidewalks, tree branches, sidewalks and the like.
In U.S. Pat. No. 3,494,727, Rapaport describes imbedding lead and copper chips of visible size into the surface of roofing shingles during manufacture. This procedure meets the aesthetics objection in the treatment of rooftop moss but would require re-roofing existing buildings at substantial expense, not to mention the increased cost of producing such roofing material. What if the metals rolled down over the roof? Moreover, this proposal is limited to treatment of rooftops with composition shingles and thus affords no solution to the problems of suppressing moss growths on other roofing materials, patios, trees, driveways, buildings and lawns.
Accordingly, a need remains for an effective method for killing moss on rooftops, building, lawns, trees, patios, sidewalks, and driveways which is inexpensive, easy to apply, fast-acting, long-lasting and additionally lacks the drawbacks of prior methods and also is not made from a chemical process of metals mixed with acids that form a salt that can burn and leach into the soil and burn roots.